Electric motor current controller with negative sequence harmonic suppression

Abstract

A method (as implemented in a current controller) is provided for higher bandwidth operation based on minimized interference between positive and negative components of a current controller, where the method may be performed without additional filtering on measured currents to isolate positive and negative current components. The method involves: identifying one or more error signals operated on by a positive sequence controller; transforming the one or more error signals into at least one negative sequence reference frame associated with at least one negative sequence controller; inputting transformed error signals to the negative sequence controller, where undesirable interactions between the positive sequence controller and negative sequence controller is minimized by sharing error signals.

The invention claimed is: 
     
       1. A method as implemented in a current controller for higher bandwidth operation based on minimized interference between positive and negative components of a current controller, the method performed without additional filtering on measured currents to isolate positive and negative current components, the method comprising:
 identifying one or more error signals operated on by a positive sequence controller; 
 transforming the one or more error signals into at least one negative sequence reference frame associated with at least one negative sequence controller; 
 inputting transformed error signals to the negative sequence controller, and where undesirable interactions between the positive sequence controller and negative sequence controller is minimized by sharing error signals. 
 
     
     
       2. The method of  claim 1 , where the current controller is for a motor. 
     
     
       3. The method of  claim 2 , where the motor is any of the following: a linear and rotary electric motor or an induction motor. 
     
     
       4. The method of  claim 1 , wherein transforming the identified error signals into at least one negative sequence reference frame associated with at least one negative sequence controller is via a rotational transform. 
     
     
       5. The method of  claim 1 , wherein the method comprises the step of computing the one or more error signals by taking a difference between measured and commanded currents. 
     
     
       6. The method of  claim 1 , wherein the one or more error signals operated on by the positive sequence controller are transformed into the at least one sequence reference frame and input to the at least one negative sequence controller with at least one targeted harmonic set by a harmonic factor value. 
     
     
       7. The method of  claim 6 , wherein the harmonic factor value is picked to suppress a positive or negative sequence harmonic caused by phase imbalance. 
     
     
       8. A method as implemented in a current controller for higher bandwidth operation based on minimized interference between positive and negative components of a current controller, the method performed without additional filtering on measured currents to isolate positive and negative current components, the method comprising:
 identifying one or more error signals operated on by a positive sequence controller; 
 transforming the one or more error signals into at least one negative sequence reference frame associated with at least one negative sequence controller and input to the at least one negative sequence controller with at least one targeted harmonic set by a harmonic factor value; 
 inputting transformed error signals to the negative sequence controller, and where undesirable interactions between the positive sequence controller and negative sequence controller is minimized by sharing error signals. 
 
     
     
       9. The method of  claim 8 , where the current controller is for a motor. 
     
     
       10. The method of  claim 9 , where the motor is any of the following: a linear and rotary electric motor or an induction motor. 
     
     
       11. The method of  claim 8 , wherein transforming the identified error signals into at least one negative sequence reference frame associated with at least one negative sequence controller is via a rotational transform. 
     
     
       12. The method of  claim 8 , wherein the method comprises the step of computing the one or more error signals by taking a difference between measured and commanded currents. 
     
     
       13. The method of  claim 8 , wherein the harmonic factor value is picked to suppress a positive or negative sequence harmonic caused by phase imbalance. 
     
     
       14. The method of  claim 8 , wherein the method comprises the step of computing the one or more error signals by taking a difference between measured and commanded currents. 
     
     
       15. A method as implemented in a current controller for higher bandwidth operation based on minimized interference between positive and negative components of a current controller, the method performed without additional filtering on measured currents to isolate positive and negative current components, the method comprising:
 identifying one or more error signals operated on by a positive sequence controller; 
 picking a harmonic factor value to suppress a positive or negative sequence harmonic caused by phase imbalance; 
 transforming the one or more error signals into at least one negative sequence reference frame associated with at least one negative sequence controller and input to the at least one negative sequence controller with at least one targeted harmonic set by the harmonic factor value picked to suppress the positive or negative sequence harmonic caused by phase imbalance; 
 inputting transformed error signals to the negative sequence controller, and where undesirable interactions between the positive sequence controller and negative sequence controller is minimized by sharing error signals. 
 
     
     
       16. The method of  claim 15 , where the current controller is for a motor. 
     
     
       17. The method of  claim 16 , where the motor is any of the following: a linear and rotary electric motor or an induction motor. 
     
     
       18. The method of  claim 15 , wherein transforming the identified error signals into at least one negative sequence reference frame associated with at least one negative sequence controller is via a rotational transform.